The IPS (namely In Plane Switching) mode type liquid crystal display apparatus has been placed on the market due to its excellent characteristics such as minimum variation in luminance at any viewing angle and minimal decline in response speed in halftone mode in the liquid crystal mode of the liquid crystal display apparatus. The IPS type liquid crystal display apparatuses are exemplified by an FFS (namely Fringe Field Switching) and an FLC (namely Ferroelectric Liquid Crystal) mode apparatuses, in addition to the IPS mode apparatus.
In the IPS type liquid crystal display apparatus, a retardation film and a polarizing plate protective film located between the liquid crystal cell and polarizer are intended to improve the viewing angle and to reduce color shift. A great difference is exhibited when compared with a TN (namely Twisted Nematic) type liquid crystal and a VA (namely Vertical Alignment) liquid crystal.
In Patent Document 1, a technique is proposed, for example, when a retardation film wherein Rt is −30 nm and Ro is 130 nm is used on the viewing side of the liquid crystal cell, and a polarizing plate protective film wherein both Ro and Rt are virtually zero, is used on the backlight side, then the color shift and corner unevenness (namely light leakage) are reduced.
In the method disclosed in the Patent Document 1, in addition to the Ro and Rt being virtually zero, the physical properties of the film in the mechanical direction and direction perpendicular thereto, among others, the tensile modulus of elasticity, storage elastic modulus, photoelastic coefficient, and dimensional stability, are made equivalent in three directions. This arrangement is claimed to be very effective in minimizing light leakage particular due to ambient temperature and humidity.
However, the aforementioned techniques are not very effective in enhancing performance such as front contrast (meaning axis view contrast), as well as in reducing color shift and corner unevenness (namely light leaking). Thus, IPS liquid crystal display apparatus which does not use a retardation film on the viewing sides of the liquid crystal cell are available on the market in greater numbers.
In a known method of improving the color shift, a cellulose ester film wherein both Ro and Rt are virtually zero is used as a double polarizing plate protective film located between both polarizers, sandwiched in turn between them and a liquid crystal cell, without a retardation film being used, as shown in Non-Patent Document 1.
However, this method has been insufficient to meet all the requirements of reduced color shift, light leakage and front contrast.
The IPS and improved FFS (namely Fringe Field Switching) modes exhibit the problems that a specific black matrix of the pixel called “gritty feel” or “display unevenness” that cannot be observed in the VA (namely Vertical Alignment) or TN (namely Twisted Nematic) mode, and a feel of graininess resulting from minute transparent electrode patterns which are observed in the IPS and FFS.
[Patent Document 1] Unexamined Japanese Patent Application Publication No. 2006-18245
[Non-Patent Document 1] Hajime Nakayama et. al. (FUJI PHOTO FILM CO., LTD.) IDW/AD '05 pp. 1317-1320
[Non-Patent Document 2] Konica Technical Report Vol. 14, pp. 77-78 (2001)